Compared with the traditional large-scale container security system, a small-scale goods baggage security inspection system (briefly called “goods machine”), as a civilian security product, appears more complex and diverse working environment, thereby the detector as its core component should have an excellent environmental adaptation. In the past, some goods machine manufacturers sealed the L-shaped detector case (a detector is mounted therein), and added a desiccant into the L-shaped detector case for moisture proofing. Afterwards, since the cost of the goods machine inspection system is taken into consideration, it is generally required that the detector has a determined moisture proof capability to reduce the cost of designing and manufacturing the L-shaped detector. Therefore, the goods machine detector manufacturers improve moisture proofing, dust proofing and salt mist proofing (“three-proofing”) of the detector by brushing three-proofing liquids thereon, which, however, brings problems of physical protection and safety for the operators. Recently, a low pressure chemical deposition method is used for depositing a poly-p-xylene film. The poly-p-xylene film has excellent three-proofing capability, but its operation is complex, and the device for applying the method is expensive, and the cost is high, so that the method is very difficult to be popularized in civilization three-proofing.